Manufacture of sheet-metal tubing



D," A, RITG H1B'. facturel of Sheet-Metal Tubing..

,228. Patented Feb. 3, 1880 lUNIT-en v DAVID A. RITCHIE, OF lCHELSEA,MASSACHUSETTS;

.MA'NUFACTURE OF SHEE'TJMETAL TUBING.

SPECIFICATION 4,folmllg part OfInetters PateVNO. '(224,228, `dated`Febrtlal'y 3, 1880.

vApplication led June 6, 1879.

To all whom Muay concern Be it known that I, DAVID A. RITCHIE, ofV

Figure 1 is a perspective view representingV apiece of my improvedsheet-metal tubing in the processof construction. Fig. 2 isa sectiontaken on the line of the seam, enlarged. Fig. 3 is a transverse sectionon the linea: vof Fig. 1.

My invention relates tol that class of sheet.- metal tubing formed byWinding astrip spirally around a mandrel; and'it consists in a spirally-Wound sheet-metal tube in Which one edge of the strip is provided Withtongues or projections formedl by punching and striking up the metal Vatsuitable intervals, the lother edge of the strip having slits orapertures through which the tongues pass as one edge of the stripoverlaps the other in the operation of winding it spirally around themandrel, the ton gues'or projections bein g'afterward clinched orlattened down on the outside of the seam in such a manner as to hold theedges of the strip rmly together and prevent any liability oftheirseparation, thus insuring a tight joint.

To enable others skilled in the art to understand and use my invention,I will proceed to describe the manner in which I have carried it out.

In the said drawings, A represents a strip of sheet lnetal of therequired width, which, as it is fed through a machine adapted for thepurpose, is Wound spirally around a mandrel or former. One edge, 5, ofthe strip A, as it passes through the machine, and before it is Wound onthe mandrel, is punched by suitable mechanism in such a manner astostrike up tongues orprojections b at short'distances apart, thesetongues being left at right angles with the surface ot' thestrip, theholes c from which the metal is punched necessarily'corresponding insize and shape to the tongues. In the opposite edge b of the strip A arepunched, at the same dista-nce apart as the tongues b, a series ofnarrow slits or apertures, d, of such size and shape and in sucha-position as to allow the tongues b to pass up through them as the edgeb is brought down onto and overlaps the edge 5 (see Fig. l) in theoperation of Winding the strip A on the mandrel. A pressure-roll orother suitable device now passes over the seam and clinchesor lattensdown thel tongues b onto the outside of the edge b, as seen in Fig. 1,which completes the operation, the two edges of the strip being heldrmly and immovably together by the clinched tongues or projections,Which thus form a cheap, simple, and

effective fastening, the several operations ot' winding the strip,striking up the tongues, forming the apertures for their reception, andclinching them down being'all performed during a single passage of thestrip through a machine, many advantages being thus presented over theordinary method of uniting j the edges of a strip of metal by means ofseparate rivets, which are more costly and involve the expenditure ofadditional time and labor in their application, besides leaving headsor'projections on the inside of the pipe, which, if of small diameter,is liable to be obstructed by the accumulation of dirt on theseprojections.

The edge b'of the strip A is provided, as

usual, with 'an oi'set, 7, which causes thejoint to be flush on theinside of the pipe, so as to offer no obstruction.

In practice I prefer to exert a very heavy pressure in clinching downthe tongues b, so as to embed or force them into the surfaceA ot' themetal on which they are laid, which causes the under surface of theoverlapping edge b ofthe strip to be pressed out, as seen in Fig. 2,into the apertures c, which lie directly beneath, and which are thusiilled up flush, causing the under surface of the edge 5 to present aperfectly smooth and even surface, While the joint is renderedadditionally secure.

I do not confine myself to the form or size of the tongues, as they maybe of any suitable shape and size.

Sheetme'tal lubin g constructed a-s above described is well adapted forwater and hot-air conductors, stove-pipes, speaking-tubes, and variousother purposes, and may be galvanized or tinned, if desired, to renderthe seam or joint perfectly tight.

What I claim as my invention, and desire to secure by Letters Patent,is-

IOO

which one edge of the strip A is provided with to force thecorresponding portion of its under 15 tongues or projections b, punchedor struck up surface into the apertures c in the piece of therefrom, andthe other edge with eorrespondmetal beneath7 from which the tongues areing slits or apertures d, through which the punched, substantially asand for the purpose 1. A spirztlly Wound sheet-metal tube in l bedded inthe outer surface of' the metal, so as tongues pass as one edge of thestrip overlaps described.

and is laid down upon the other in the opere- Wit-ness my hand this 4thday of June7 A. 2o tion of Winding, the tongues being afterward D. 1879.

clinched or flattened down to secure the over DAVID A RITCHIE lappingedges of the strip together und form the joint, substantially asdescribed.

2. In a joint forsheet-metal tubing made as described, the tongues b,pressed into or em- In presence of- P. E. TESGHEMACHER, W. J CAMBRIDGE.

